STATUS OF THE CUORE0 AND CUORE EXPERIMENTS

Transcription

1 STATUS OF THE CUORE0 AND CUORE EXPERIMENTS O.Cremonesi INFN Sez. Milano Bicocca 1

2 STATUS OF THE CUORE0 AND CUORE EXPERIMENTS O.Cremonesi INFN Sez. Milano Bicocca Outine: Scientific goal Experimental setup Status CUORE-0 Conclusions 1

3 CUORE Cryogenic Underground Observatory for Rare Events Closely packed array of 988 TeO 2 crystals cm 3 (750 g) 741 kg TeO 2 granular calorimeter 600 kg Te = 203 kg 130 Te 19 towers 13 planes each 4 crystals each 80 cm Calorimetric experiment on 130Te neutrinoless DBD Background ΔE T 1/2 <m ee > c/kev/kg/y kev y R(QRPA) 1 np(qrpa) 2 ISM 3 IBM Dark Matter search potential F.Bellini talk 1 Šimkovic et al., PRC 77 (2008) Civitarese et al., JoP:Conference series 173 (2009) Menéndez et al., NPA 818 (2009) Barea and Iachello, PRC 79 (2009) Single cryogenic setup (Twork=10-15mK) Complex system of radiation shields Mechanical decoupling system Detector calibration system Underground laboratory (LNGS) 2

4 The CUORE Collaboration 3

5 TeO2 bolometers evolution ΔE = 6.2 ± 2.5 kev (~0.3% FWHM) Bkg = 0.169±0.006 c/kev/kg/y CUORICINO 40 kg ( ) CUORE-0 (2012) CUORE 1 ton (~2014) T 1/2 0ν (y) > y (90% CL) Astroparticle Physics 34 (2011) Extensive study of background sources M bb < ev NME from F.Simkovic et al. Phys.Rev. C77 J.Suhonen et al. Int.Jou.Mod.Phys. E17 J.Menendez et al. Nucl. Phys. A818 J.Barea et al. Phys. Rev. C79 Careful design and construction of the setup Hut and infrastructures Detector Crystals Structure Assembly Cryostat and shields Calibration system Electronics 4

6 ββ0ν experimental sensitivity S 0 1/2 (m ee) / i.a. A Isotope choice 1 p G 0 M 0 r bkg 4 Mass Energy resolution Background level Long measure time ββ candidate: 130 Te Q kev E M t meas Source Mass: 206 kg 130 Te N ββ 9.6 x10 26 Projected Bkg: 0.01 c/kev/kg/y Resolution: ~ 5 Sensitivity T 1/2 0ν : 1.6x10 26 y in 5 y Deep underground location Bolometric approach Large mass array Material selection Severe control of procedures Stable operating condition over several years Sensitivity <m ee >:<m ee > < mev in 5y (IH) 5

7 The LNGS underground facility CUORE hut (New Building) A24 NE Underground facility Average depth ~ 3650 m.w.e. Cuoricino/CUORE-0 hut Factor 10 6 reduction in muon flux to ~ µ/(s cm 2 )

8 The CUORE TeO2 bolometers Heat sink (8-10 mk) Weak Thermal coupling Absorber Crystal (C) Thermometer Cu holder PTFE supports (G) TeO 2 crystal NTD Ge sensor Incident radiation (E) ΔT = E C Pros: - good energy resolution - different sources could be investigated - high efficiency (internal sources) τ = C G T 1 s Cons: - no dead layer - low temperature tech required - slow pulses 7

9 Background contributions Largest available statistics: Cuoricino ROI But a lot of information comes also from dedicated R&D bolometric measurements in an R&D cryogenic LNGS 8

10 R&D and QC tests TTT (Three Tower [cleaning] Test) RAD (RADioactivity study setup) CCVR (CUORE crystal validation runs) No way of measuring directly the background level in the ββ0ν ROI Background model needed 9

11 c/kev/kg/y Background model MC: the background in CUORICINO is due to degraded alpha particles which release only part of their energy in the detector (surface contamination) 10 2 γ + γ 60 Co Q 0νββ (2527keV) energy [kev] 0νDBD region = / c/kev/kg/y (ainticoincidence spectrum, 5x5x5 cm 3 crystals) C.Arnaboldi et al ± 10 % 232 Th in cryostat (γ) 10 ± 5 % TeO 2 surface (α) 50 ± 20 % Cu surface (α) C.Arnaboldi et al. Phys. Rev C 78 (2008)

12 Background budget Source CUORE in the ROI c/(kev kg y) Source of data Cosmogenic activation of crystals (bulk) ~ NAA + MC Gold wires ( 232 Th and 238 U) (bulk) < Bolometric test + HPGe Copper frames ( 232 Th) (bulk) < HPGe + NAA + MC 232 Th in the Roman lead shield (bulk) < Bolometric + HPGe Muon interactions (bulk) ~ Measured fluxes + MC TeO 2 crystals surface activity < Bolometric tests (CCVR) + MC Surface activity of the mounting structure < Test on small tower + MC < Test on small tower + MC If contamination in the R&D run are due to surface contamination of copper structure If contamination in the R&D run are due to 210 Pb contamination of PTFE (unlikely) mutually exclusive hypotheses! new measurement in progress F.Alessandria et al. [CUORE coll.] C.Arnaboldi et al. Phys. Rev. C 78 (2008) F.Bellini et al. Astr.Phys. 33 (2010) 169 F.Alessandria et al. [CUORE coll.]

13 Background budget Source CUORE in the ROI c/(kev kg y) Source of data Cosmogenic activation of crystals (bulk) ~ NAA + MC Gold wires ( 232 Th and 238 U) (bulk) < Bolometric test + HPGe Copper frames ( 232 Th) (bulk) < HPGe + NAA + MC 232 Th in the Roman lead shield (bulk) < Bolometric + HPGe Muon interactions (bulk) ~ Measured fluxes + MC TeO 2 crystals surface activity < Bolometric tests (CCVR) + MC Surface activity of the mounting structure < Test on small tower + MC < Test on small tower + MC Conservative If contamination values in the R&D run are due to If contamination in the R&D run are due to 210 Pb surface contamination copper structure contamination of PTFE (unlikely) Different depth profiles of surface contaminations compared and largest values quoted mutually here exclusive hypotheses! Upper limits new measurement in progress Attribute all events in the target region as due solely from a certain source F.Alessandria et al. [CUORE coll.] C.Arnaboldi et al. Phys. Rev. C 78 (2008) F.Bellini et al. Astr.Phys. 33 (2010) 169 F.Alessandria et al. [CUORE coll.]

14 CUORE sensitivity Background goal of 0.01 c/kev/kg/y T 1/2 = 1.6 x y m ββ = mev 12

15 CUORE sensitivity Background goal of 0.01 c/kev/kg/y T 1/2 = 1.6 x y m ββ = mev The large mass and excellent energy resolution, make CUORE competitive to sound the IH region down to mev 12

16 CUORE experimental setup Custom cryogenic LNGS. Improved shielding and material selection. High efficiency in background rejection, due to the packed geometry: minimum lead thickness surrounding the detector ~ 36 cm No cryogenics liquids: better duty cycle Mechanical suspension of the detector assembly completely independent from the refrigeretor structure: better control of noise induced by vibrations Severe control of the radioactivity of the set-up Embedded in the setup (after a severe control of the radioactivity of the materials): Cryo-free dilution refrigerator (Leiden Cryogenics) Roman Lead (no 210Pb) cold shield Detector and Pd shiled suspension Calibration system 300K plate Pulse Tube 40K plate Roman Pb shields Detector Detector suspension 4K plate (IVC) Mixing Chamber 13

17 Detector Calibration System 12 gamma source wires o 232 Th: thoriated tungsten wire o 56 Co: proton activated Fe wire Minimize down time but rate at each crystal not exceeding 150 mhz Stringent heat load requirement 14

18 An improved tower design Copper Frame: Heat bath Background source Teflon holders The weak thermal link Reduce vibra\on noise 15

19 CUORE tower assembly line Set of specially designed Glove Boxes Rn free atmosphere strict control of materials reproducible protocol Mechanical Cabling Bonding Storage Completed Summer

20 CUORE status & schedule Detector Crystals, almost completely delivered at LNGS Copper parts machining and cleaning are progressing regularly Tower assembly line was completed in 2011 and tested on CUORE0. Ready to start for the CUORE tower assembly in November 2012 Radon abatement system installed CUORE Hut, and most of all the infrastructures are ready Cryogenics Dilution unit delivered to LNGS. Performance better than expected. 3 (of 6) cryostat vessels tested and delivered at LNGS Commissioning of the cryogenic setup started on July 2012 Crystals 12/12 Thermistors 13/03 Cleaned Cu parts 13/12 Cryogenics 13/12 Tower Assembly 14/04 Detector insertion 14/07 Cool Down Fall 2014 O.Cremonesi - 10/09/2012 Otranto 17

21 Detector parts Teflon and Copper parts almost completed: Copper cleaning underway As of August 2012 TeO2 SICCS close to completion NTD s: 695 of 1250 already delivered 18

22 CUORE-0 Critical points in the way of CUORE experiment: uniformity of the detector array control of possible recontamination during the detector construction CUORE-0: first tower from the CUORE assembly line operated as a stand alone experiment in the CUORICINO cryostat CUORE-0 goals: - full test and debug of the new CUORE assembly line high statistics check of the improved uniformity of bolometric response identify which operations are critical for the success of CUORE reveal flaws and inefficiencies in the assembly procedures - thorough exercise of the analysis framework 19

23 CUORE0 construction Mechanical assembly Sensors & heaters gluing semi-automated system Sense wire (ball) bonding 50 µm gold wire direct bonding on final detector 20

24 3 mm Crystal-Sensor coupling Robotic gluing for Uniformly sized Repeatable Controllable glue spots (and coupling) 21

25 Mechanical assembly 22

26 Cabling 23

27 Wire bonding

28 Storage 25

29 CUORE0 installation CUORE-0 assembly already gave us the opportunity to test and fix the procedures and the systems to realize the CUORE detector: a complete CUORE tower can be assembled in less than 4 weeks Other innovative changes (e.g. sense wires) are also being tested 26

30 CUORE-0 status First Pulse 24/8/2012 T ~ 14 mk CUORE-0 is in the pre-operation phase In August 2012 the detector reached base T of about 8 mk All the active channels survived the cool-down CUORE collaboration is not ready to release information on resolution and detector performances but these will come very soon 27

31 CUORE-0 status we already learned that: the assembly line works properly the thermal contractions didn t cause problem to the tower wires the bonding connections survive to thermal cycles the thermal conduction of the new tower wires has to be taken into account for CUORE detector First Pulse 24/8/2012 T ~ 14 mk CUORE-0 is in the pre-operation phase In August 2012 the detector reached base T of about 8 mk All the active channels survived the cool-down CUORE collaboration is not ready to release information on resolution and detector performances but these will come very soon 27

32 CUORE-0 status we already learned that: the assembly line works properly the thermal contractions didn t cause problem to the tower wires the bonding connections survive to thermal cycles the thermal conduction of the new tower wires has to be taken into account for CUORE detector First Pulse 24/8/2012 T ~ 14 mk based on CUORE-0 experience a detailed plan for the 19 CUORE towers has been prepared, aiming at Minimizing manpower, cost, and duration Maximizing efficiency CUORE-0 is in the pre-operation phase Preserving quality control In August 2012 the detector reached base T of about 8 mk the start of the full plan is expected by the beginning of November All the active channels survived the cool-down CUORE collaboration is not ready to release information on resolution and detector performances but these will come very soon 27

33 CUORE0 sensitivity F. Alessandria et al. [CUORE coll.] Limited by bkg from cryostat contamination Background: c/kev/kg/y range If 0.05 c/(kev kg y), expected 2-year sensitivity is T 1/2 = 5.9 x %CL (CUORICINO: T 0ν > y) m ββ = mev Significance level at which CUORE-0 can observe a DBD signal consistent with the claim in 76 Ge (KK-HK), assuming 0.05 c/kev/kg/y background The inner band corresponds to the best-fit value of the claim; the range arises from the 1σ range of QRPA NME calculations in A. Faessler et al., Phys. Rev. D79 (2009) The outer band also includes the 1σ error on the 76 Ge claim 28

34 Cryogenics The acceptance tests of the 2 vacuum tight chambers (300K and 4K) of the CUORE cryostat have started at the end of May 2012 The test was comoleted mid July and the chambers delivered at LNGS by the end of July. Since then we are following a detailed plan of commissioning of the cryogenic system which will last for the another 1.5 years The CUORE LNGS (hall B) 4K construction company (SIMIC) O.Cremonesi - 24/09/2012 NPB Shenzhen 29

35 Vacuum SIMIC Cooldown preparation Superinsulation 4k insertion 30

36 Setup LNGS 300K plate 4K plate Detector suspension system 300K & 40K plates 31

37 LNGS 4K vessel installation operations under the 300K plate 32

38 Conclusions With ~200 kg of 130Te and a resolution of 5 KeV FWHM, CUORE has the potential to explore the inverted mass hierarchy of neutrino mixing CUORE-0 has demonstrated that the collaboration can face the challenge of assembling the ~1000 CUORE bolometers (~10 k pieces) in extremely clean conditions CUORE towers assembly will start in a couple of months. Cryogenics commissioning was finally started in July It will continue for the whole CUORE operation will start in 2014 CUORE-0 prototype has been successfully installed (in the CUORICINO cryostat) and is presently in the pre-operation phase. It will start to collect data very soongive us answers very soon. 33